In attempting to reduce the emissions, a wide array of industrial applications have implemented significant changes through their combustion systems, including the use of oxygen-enriched combustion. The benefits of replacing air with oxygen include NO.sub.x and particulate reduction, improved production rates, fuel savings, and the reduction of capital requirements for furnace rebuilding. However, burner systems used for oxygen combustion often perform poorly and suffer such problems as corrosion, material build-up, and low flame luminosity. Most oxy-fuel burners are water cooled, thus requiring frequent maintenance to prevent loss of cooling and subsequent catastrophic failure of the burner. Also, the oxy-fuel flames produced by such burners have much smaller flame coverage than manufacturers are used to having with air-based combustion systems. In some applications, this results in local overheating and disruption of normal furnace operation.
U.S. Pat. Nos. 5,199,866, 5,256,058, and 5,346,390 pertain to burners and methods for producing luminous flames at low flow rates. According to the patentees, such flames are produced by surrounding a core of a fuel rich phase with an oxygen rich phase. It has been found that such burners have low flame luminosity at higher burning rates. In general, increasing the size of the cylindrical or axy-symmetrical shaped burners yields only minor increases in flame luminosity. Flames having low luminosity cannot release heat efficiently and produce high flame temperatures which in turn yield high NO.sub.x emissions in furnaces that are not well sealed or when operating with fuels or oxidizers containing nitrogen. Flame coverage is limited to the cylindrical flame shape produced with these and other axy-symmetric oxy-fuel or oxygen enriched air burners.
U.S. Pat. No. 5,302,112 discloses a flat flame burner which produces the flat flame by having two independent fuel jets intersect inside a furnace to produce a flame flattening effect.
The foregoing are attempted solutions at a frequently encountered problem with full or partially combustion-heated furnaces which result in high emission of pollutants, such as NO.sub.x i, CO.sub.2, and particulates. Regulations of such emissions are becoming more stringent and the regulated industries must change their operations to comply with the emission limits.